Jurors in the trial of former state treasurer Timothy P. Cahill declared themselves hopelessly deadlocked this afternoon, leading a Superior Court judge to declare a mistrial in a case that was the first major test of a 2009 anti-corruption law.

Attorney General Martha Coakley said at a news conference less than two hours later that she hadn’t decided yet whether to retry Cahill.

“I continue to believe in the strength of this case and the strength of our justice system. We are reviewing our options going forward,” she said.

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The Suffolk Superior Court jury returned to the ninth-floor courtroom in the Boston courthouse shortly before 2:30 p.m. and brought an end to deliberations that had stretched over seven days and an estimated 40 hours of closed-door conversations between the 12 people.

The courtroom was packed with Cahill’s relatives and reporters. When the deadlock was announced and the mistrial declared by Judge Christine Roach, Cahill’s wife, Tina, began to weep. Later, she said she believed the case had been “detrimental to the political system.’’

Cahill, who turned to supporters in the first row and exchanged hugs, called the outcome a “total vindication’’ for his claim that he acted in the interest of the state lottery, not his political career, when he approved a $1.5 million lottery ad blitz while running as an independent candidate for governor in 2010.

Asked what he would be doing tonight, his first in a long time without the prospect of a prison sentence hanging over his head, Cahill responded, “Probably rakin’ leaves.’’

“The jury’s inability to agree on a verdict in this case after six and one-half days of careful consideration confirms the opinion we’ve had from the start that matters like these are more appropriately resolved in a civil setting by the State Ethics Commission than they are in a criminal courtroom,” Cahill defense attorney Brad Bailey said in a statement.

Coakley, after thanking the jurors for their service, said at her news conference that “I believe that the only way we will change things in this Commonwealth is to be willing to bring cases of public corruption when we believe we have the evidence. ... I believe that our office has done the right thing by bringing this case.”

One juror, who would not give his name, told reporters, “It’s a complicated process, and it’s a complicated law. There was a lot of information. The hurdles you have to cross in order to prove it beyond a reasonable doubt — for some people — were not crossed.’’

Asked if he thought justice was done, the juror paused and said, “In the sense that there was a decision, yes.’’

Cahill and his former campaign manager, Scott Campbell, were both charged with two counts of conspiracy under a 2009 state ethics law passed in response to a corruption scandal involving former House speaker Salvatore F. DiMasi, who is now serving a federal prison sentence in an unrelated corruption case. The Cahill case was the first significant test of the new law, which criminalized conduct that had before been considered unethical.

Coakley defended the new law. “The one thing the public demands, respects, wants is that their taxpayer dollars are not misused. If evidence comes to my attention that taxpayer dollars have been used, then I have to take appropriate action,” she said.

On Tuesday, the jury acquitted Campbell and also told the judge they could not reach a unanimous verdict for the former state treasurer. The judge then gave the jury what attorneys called the “dynamite’’ charge designed to break any deadlock.

But the jurors, after resuming deliberations today, said again that they could not reach agreement, and Roach dismissed them with her thanks.

Earlier today, Roach today released the text of the notes sent to her by the jury at the request of the Globe.

The notes depicted a jury struggling to apply the law to the facts of the Cahill case, which was based on a trail of e-mails, text messages, and phone records that allegedly showed Cahill’s political operatives discussing the lottery ads with executives at Hill Holliday, the Boston agency that was being paid state money to handle the lottery’s ad account.

One juror laughed when asked if Coakley should retry Cahill. “None of us on this jury ever want to think about this case again,” the juror said.

At her news conference, Coakley declined to put a price tag on prosecuting the case and wouldn’t say whether she felt the failure to win a conviction would hurt her political career.